1. Field of the Invention
The present invention relates to a computer system and a booting method therefor and a server used for the same, and more particularly to a system for booting a computer using a program loaded through a network.
2. Description of the Prior Art
In general, the order of processing when booting a computer is that first a hardware is initialized, next an operating system (hereunder, referred to as “OS”) is started up, and finally required application programs are launched.
Here, upon starting up the OS and the application programs excluding initialization of the hardware, first, a processing which reads these programs is performed, and next the initialization processing described in the programs is performed. After the initialization processing is completed, the operation processing which is the function of the original purpose of the programs can be carried out.
Specifically, processing to read the OS is performed by an IPL (Initial Program Loader) which carries out operations to load the OS program from a memory. Loading is also performed from a memory or storage when loading an application program. Incidentally, in this case, a loading subject is the OS. At this time, in addition to a method whereby a program is loaded from a local hard disk drive (HDD) of the computer, a method is available in which a program is loaded through a network. An operation in which booting a computer system is performed by loading the OS program through the network is referred to as “network boot” (for example, see Non-Patent Document 1).
By using the network boot, even if a computer does not have a local HDD, the system can be booted by loading the OS program from a server which supplies the programs. Therefore, OS and application programs and the like which had been installed on the local HDD of respective computers can be managed on the centralized server. This allows the programs to be kept updated to the most recent versions to enable prevention of security holes and computer virus attacks. In this case, even if the number of computers increases there is no additional cost required to manage the programs. Further, by providing programs of a plurality of systems on the server, it is possible to set on the server which system is to be used to boot respective computers. Because of such characteristics, in a system providing service by geographically concentrating a large number of server computers, the network boot is considered a favorable technique for so-called deployment in which a new server is added to improve response to requests when the load of each server rises due to an unexpected increase in requests.
However, although the network boot has these kinds of advantages, the network boot requires longer time to read programs because the programs are loaded from the server through the network. Thus, one problem is that the time required for booting is long in comparison to a conventional booting method which loads programs from a local HDD. Therefore, technology which speeds up booting of a computer system by the network boot is important.
As a conventional high-speed booting method for computers which does not rely on the network boot, a technique is known that uses a boot-up main memory image. This method performs booting by utilizing the fact that as long as the settings and configuration of the hardware, OS and application programs are not changed, the same operations are performed each time in which system initialization processing is carried out, and thus the state of the contents of the main memory immediately after boot-up is roughly the same each time. Therefore, in this method, the boot-up main memory image is stored in a local storage and loaded in that state to be written into the main memory at boot-up.
One example of this kind of high-speed booting method is disclosed in Patent Document 1. In the method disclosed in this document, a backup memory or a disk file is provided for backup, and the boot-up main memory image is stored in the memory or the disk file. At the time of booting and rebooting, memory copying is carried out consecutively from the memory or the disk file to the main memory, and as soon as copying of the boot-up main memory image onto the main memory is completed the system can operate. The Patent Document 1 also contains a description regarding a method for generating the boot-up main memory image.
[Non-Patent Document 1] Hal Stern, “NFS & NIS”, ASCII Corporation, Dec. 1, 1992, pp. 219-232.
[Patent Document 1] Japanese Patent No. 2772103 (Japanese Patent Laid-Open No. 03-278126)